Liquid electrophotographic ink having improved durability

Abstract

The present disclosure is drawn to a liquid electrophotographic ink, comprising a carrier liquid, and a pigment-polymer blend composition dispersed in the carrier liquid, the pigment-polymer blend composition comprising a pigment and a polymer blend of three distinct polymers. The polymer blend can comprise a first polymer having a melt flow rate of about 20 to about 70 g/10 min and a Vicat softening point of about 60° C. to about 70° C., a second polymer having a melt flow rate of about 80 to about 120 g/10 min, and a third polymer having an acidity of about 160 to about 230 mg KOH/g and a melt flow rate of at least 500 g/10 min. The liquid electrophotographic ink is typically formulated for printing from a liquid electrophotographic printer.

What is claimed is: 
     
       1. A liquid electrophotographic ink, comprising:
 a) a carrier liquid, and 
 b) a pigment-polymer blend composition dispersed in the carrier liquid, the pigment-polymer blend composition comprising a pigment and a polymer blend of at least three distinct polymers, the polymer blend comprising:
 i) a first polymer having a melt flow rate of about 20 to about 70 g/10 min and a Vicat softening point of about 60° C. to about 70° C., 
 ii) a second polymer having a melt flow rate of about 80 to about 120 g/10 min, and 
 iii) a third polymer having an acidity of about 160 to about 230 mg KOH/g and a melt flow rate of at least 500 g/10 min, 
 
 wherein the liquid electrophotographic ink is formulated for printing in a liquid electrophotographic printer. 
 
     
     
       2. The liquid electrophotographic ink of  claim 1 , wherein the polymer blend further comprises an incompatible wax. 
     
     
       3. The liquid electrophotographic ink of  claim 2 , wherein the wax is selected from the group consisting of polyethylene, oxidized polyethylene, polyolefins including blends thereof, and mixtures thereof. 
     
     
       4. The liquid electrophotographic ink of  claim 1 , wherein the polymer blend further comprises about 2 to about 20 micron particles of polytetrafluoroethylene. 
     
     
       5. The liquid electrophotographic ink of  claim 1 , wherein the first polymer has an acidity of about 90 to about 130 mg KOH/g. 
     
     
       6. The liquid electrophotographic ink of  claim 1 , wherein the first polymer is selected from the group consisting of ethylene-vinyl acetate (EVA) copolymers; copolymers of ethylene and an ethylenically unsaturated acid of either acrylic acid and methacrylic acid; copolymers of ethylene, acrylic or methacrylic acid/alkyl ester of methacrylic or acrylic acid; polyethylene; polystyrene; crystalline polypropylene; ethylene ethyl acrylate; ethylene methacrylic acid copolymers which are partially neutralized with metal ions; acid modified ethylene vinyl acetate terpolymer or blends thereof; polyesters; polyvinyl toluene; polyamides; styrene/butadiene copolymers; combinations thereof; and blends thereof. 
     
     
       7. The liquid electrophotographic ink of  claim 1 , wherein the first polymer is selected from the group consisting of copolymers of ethylene and an ethylenically unsaturated acid of either acrylic or methacrylic acid; an ionomer of ethylene methacrylic acid copolymer; an ester of ethylene methacrylic acid copolymer and an acid modified ethylene vinyl acetate terpolymer; combinations thereof; and blends thereof. 
     
     
       8. The liquid electrophotographic ink of  claim 1 , wherein the first polymer is a copolymer of an ethylene and an ethylenically unsaturated acid of either acrylic or methacrylic acid. 
     
     
       9. The liquid electrophotographic ink of  claim 8 , wherein the ethylenically unsaturated acid of either acrylic or methacrylic acid comprises about 10 wt % to about 20 wt % of the copolymer. 
     
     
       10. The liquid electrophotographic ink of  claim 1 , wherein the second polymer has an acidity of about 50 to about 80 mg KOH/g and a Vicat softening point of about 60° C. to about 70° C. 
     
     
       11. The liquid electrophotographic ink of  claim 1 , wherein the second polymer is selected from resins such as ethylene-vinyl acetate (EVA) copolymers; copolymers of ethylene and an ethylenically unsaturated acid of either acrylic acid and methacrylic acid; copolymers of ethylene, acrylic or methacrylic acid/alkyl ester of methacrylic or acrylic acid; polyethylene; polystyrene; crystalline polypropylene; ethylene ethyl acrylate; ethylene methacrylic acid copolymers which are partially neutralized with metal ions; acid modified ethylene vinyl acetate terpolymer or blends thereof; polyesters; polyvinyl toluene; polyamides; styrene/butadiene copolymers; combinations thereof; and blends thereof. 
     
     
       12. The liquid electrophotographic ink of  claim 1 , wherein the second polymer is selected from the group consisting of copolymers of ethylene and an ethylenically unsaturated acid of either acrylic or methacrylic acid; an ionomer of ethylene methacrylic acid copolymer; an ester of ethylene methacrylic acid copolymer and an acid modified ethylene vinyl acetate terpolymer; combinations thereof; and blends thereof. 
     
     
       13. The liquid electrophotographic ink of  claim 1 , wherein the second polymer is a copolymer of ethylene and an ethylenically unsaturated acid of either acrylic or methacrylic acid. 
     
     
       14. The liquid electrophotographic ink of  claim 8 , wherein the ethylenically unsaturated acid of either acrylic or methacrylic acid comprises about 7 wt % to about 12 wt % of the copolymer. 
     
     
       15. The liquid electrophotographic ink of  claim 1 , wherein the third polymer has a melt viscosity lower than 1000 cps. 
     
     
       16. The liquid electrophotographic ink of  claim 1 , wherein the third polymer is selected from the group consisting of copolymers of ethylene acrylic acid; copolymer of ethylene methacrylic acid; acid modified polyethylene low molecular weight polymers; maleic anhydride modified polyethylene; and mixtures thereof. 
     
     
       17. The liquid electrophotographic ink of  claim 1 , wherein the third polymer is a copolymer of ethylene acrylic acid. 
     
     
       18. The liquid electrophotographic ink of  claim 1 , wherein the first polymer is present in the ink from about 60 wt %/solids to about 90 wt %/solids, the second polymer is present in the ink from about 5 wt %/solids to about 30 wt %/solids, and the third polymer is present in the ink from about 5 wt %/solids to about 25 wt %/solids. 
     
     
       19. The liquid electrophotographic ink of  claim 1 , further comprising a charge director. 
     
     
       20. A method of manufacturing a liquid electrophotographic ink having improved durability, comprising
 a) forming a polymer blend by processing a carrier liquid and three distinct polymers, comprising:
 i) a first polymer having a melt flow rate of about 20 to about 70 g/10 min and a Vicat softening point of about 60° C. to about 70° C., 
 ii) a second polymer having a melt flow rate of about 80 to about 120 g/10 min, and 
 iii) a third polymer having an acidity of about 160 to about 230 mg KOH/g and a melt flow rate of at least 500, 
 
 b) processing the polymer blend with a pigment and charge director to form a the liquid electrophotographic ink, 
 wherein the liquid electrophotographic ink is capable of being printed from a liquid electrophotographic printer. 
 
     
     
       21. The method of  claim 20 , wherein the polymer blend further comprises a wax that is incompatible with the polymer blend. 
     
     
       22. The method of  claim 20 , wherein the first polymer has an acidity of about 90 to about 130 mg KOH/g and the second polymer has an acidity of about 50 to about 80 mg KOH/g. 
     
     
       23. The method of  claim 20 , wherein the first polymer or the second polymer is a copolymer of ethylene and an ethylenically unsaturated acid of either acrylic or methacrylic acid. 
     
     
       24. The method of  claim 20 , wherein the third polymer has a melt viscosity lower than about 1000 cps. 
     
     
       25. A method of printing a liquid electrophotographic ink having improved durability, comprising printing the liquid electrophotographic ink of  claim 1  on a substrate using a liquid electrophotographic printer. 
     
     
       26. The method of  claim 25 , wherein the substrate includes paper.